1. Field of the Invention
The present invention relates to an optical scanning device for performing optical writing in, for example, an electrophotographic printer and, more specifically, to an optical scanning device provided with a shutter for opening/closing a laser beam exposure window with a simple structure, as well as to an image forming apparatus including the device.
2. Description of the Background Art
Image forming apparatuses such as a laser printer, a digital copy machine and a laser facsimile include an optical scanning device for writing an electrostatic latent image on a photoreceptor (electrostatic latent image carrier). Recently, as higher image quality of image forming apparatuses has been required, it becomes a problem that a laser beam exposure window of the optical scanning device becomes grimy because of toner or dust and intercepts the laser beam so that image quality degrades. Further, since size reduction of the image forming apparatuses has been desired, arrangement of optical scanning devices in the image forming apparatuses has been diversified. For example, it may be positioned lower than the photoreceptor. In such an arrangement, falling toner or dust in the image forming apparatus may dirty a dustproof glass provided on the laser beam exposure window, possibly degrading image quality.
In such an image forming apparatus, works of toner replenishment and photoreceptor exchange are necessary. If toner or dust should adhere to the laser beam exposure window during such works, image quality would be degraded. Further, during such works, a polygon mirror for laser scanning is stopped. Therefore, if laser beam emission should occur, a narrow-focused laser beam could be emitted.
In view of such problems, Japanese Patent Laying-Open No. 2-272470 (Document 1) discloses an image forming apparatus that reliably prevents leakage of laser beam to the outside on occasions possibly leading to laser beam leakage, for example, when a photoreceptor unit is taken out from the image forming apparatus for maintenance. The image forming apparatus has a laser scanning optical system, a unit including an image carrier and a mechanism for forming an image on the image carrier, and a container for recovering and storing residual toner on a surface of the image carrier, in which a shutter for intercepting laser beam from the scanning optical system is provided. The shutter is opened/closed, linked with attachment/detachment of a unit substantially integrating the image carrier unit and the toner recovery container.
Further, Japanese Patent Laying-Open No. 2007-144853 (Document 2) discloses an optical scanning device suitable for an image forming apparatus having a shutter mechanism provided between an image carrier and the optical scanning device, which does not require a large space in up-down direction in the image forming apparatus. The optical scanning device scans an object surface by emitting light flux from a light source through an exposure window of an optical housing, and the device is provided with an integral shutter member for opening/closing the exposure window, with the shutter member moved by driving means (motor) using a link mechanism.